Known active compounds with in vitro activity may not be accessible for in vivo therapy because of difficulties in delivery of these compounds. For instance, the compound may have a short in vivo half-life, rendering the compound practically useless in vivo. Similarly, a compound may be unstable in vivo, converting to an inactive compound under physiological conditions. Or alternatively, a compound may be associated with significant toxicity, rendering its in vivo use difficult. There is a need, therefore, for a method of delivering these active compounds that both maintains the activity of the compound in vivo, and directs delivery to a desired target cell, avoiding potential toxicity.